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TOPIC: December 2009


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RE: December 2009
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Three planets gather in the December twilight. The easiest to spot is Jupiter. This giant world is a bright beacon in the south-southwest sky. Mercury makes a brief appearance around mid-month low in the southwest; while very faint Neptune nestles next to Jupiter.
Mercury crosses Sagittarius during this Christmas appearance. It will hug the southwest horizon during the first week of December. Your best chance to observe this tiny world will be from Dec. 15 until Christmas.

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Solstice
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The powerful astronomer-priests who performed these measurements in past centuries knew that when the lowest-noonday-Sun and farthest-left-sunset points were observed, they had reached the darkest day. After this, the Sun would day-by-day return to its higher position in the sky; the air would eventually warm; it would soon be time to plant the new crops. Of course we should celebrate the Return of the Sun! We should also pay a substantial fee to those astronomers who had such wondrous knowledge of the world. Ah, the good old days!
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RE: December 2009
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December begins with the full moon within one degree of the Pleiades, the Seven Sisters, and ends with a ''blue moon,'' the term for a second full moon in the month. New Year's Eve will feature a partial lunar eclipse, but you will have to be in Africa or Asia to see it.
Look for Mercury, an evening star, on Dec. 24 at 5:55 p.m. Mercury will form the bottom point of an equilateral triangle with Jupiter (above and to the south) and Altair, the eye of the Eagle (above and to the west). By the end of December, Mercury will appear as a slim crescent in a telescope.

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December brings us two full moons, one on Dec. 2 and the other on Dec. 31. The second full moon in any given month is often called a "blue moon," although the meaning of the term has changed somewhat over the decades.
Under this definition, the next one occurs in August 2012.

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For you planet watchers, Jupiter is on the meridian at sunset located in Capricorn. Mars, in the house of Leo the Lion, rises around 10 p.m. with Saturn following at 1 a.m.
This is a great month for planet observing and also the Geminid meteor shower, which peaks around Dec. 13-14. Looking toward the east during this new moon time, expect to see up to 60 multicoloured meteor streaks after midnight.

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Highlights:
Winter Solstice on December 22nd. This is officially the longest night of 2009, (even though the year's earliest sunset occurs two weeks earlier).
The Geminid meteors on the night of the 13th-14th. Watch out for this reliable shower.
Capricornus, the Sea Goat: Sign of the Zodiac for birth dates between 22 December and 19 January; it is the leading constellation of the "wet" or "water" constellations. Capricornus has a symmetrical shape resembling a bikini bottom, but the stars of Capricornus are very faint with no star brighter than the third magnitude. Capricornus appears low in the southern sky (never at higher altitudes). The Tropic of Capricorn (23.5 degrees South latitude) is named after Capricornus; on 22 December (on average), the Sun is directly overhead (at the zenith) at Noon along the Tropic of Capricorn. In Mythology, the Greeks identified Capricornus with Pan, the god of nature, who was pictured as half-man, half-goat. In fear, Pan escaped the giant Typhon by leaping into the Nile River and changing his tail to that of a fish. This is the origin of the word, "panic."

There are many meteor showers this month...
The Geminid Meteors Shower Peaks on the night of the 13th-14th. A thin crescent moon does not hamper this reliable shower.
The Coma Berenicids are a poorly-known minor shower, and badly need more observing. Very swift meteors, (65km/sec). Their Radiant is at RA 11h40m Dec +25.
Ursids Meteor Shower
Peaks on the 17th. A minor shower. The peak is predicted about 2200 UT. The radiant (RA 14h28m Dec +76) is circumpolar (It never sets in northern locations). The meteors are generally slow (33km/sec) and rates are lower than the Geminids, but certainly above the background sporadic count.
The Ursids are linked with Comet 8P/Tuttle (period around 13.5 years; last at perihelion in 1994). Their peak rates can be quite variable
Also, watch out for sporadic meteors. Their rates for the Northern Hemisphere are now reaching a plateau. Expect around 12 random meteors per hour during the morning hours

Shower Activity Period Maximum Radiant Velocity ZHR


Date R.A. Dec. km/s
Cygnids
Dec 2 13.9h -12.0 19.4 82.9
Taurids Oct 30 -Nov November 3.1h -17.5d 25 16
Geminids Dec Dec 13 7.6 32.3 34.7 25.7
Ursids Dec 22 Dec 17 14.3 77.7 33.4 10.3


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